1. Field of the Invention
This invention relates to the processing of a data stream that includes the velocity and location of multiple vehicles operating on monitored lengths of highway so as to generate warnings and/or commands that will eliminate or mitigate the development of accident situations. Systems of this type must provide effective warnings or commands in a variety of crash situations. The United States Department of Transportation has defined these as including, but not limited to, "Rear-end Crash Warning and Control," "Head on Crash Warning and Control," "Passing Warning," "Backing Crash Warning," "Lateral Collision Avoidance," "Intersection Crash Warning," and the avoidance of collisions caused by "Impaired Drivers."
Systems of this type must exhibit low false alarm rates and avoid the generation of commands not warranted by developing traffic situations. High false alarm rates will result in driver loss of confidence and cause traffic delays that cannot be tolerated in congested traffic environments.
Information must be conveyed to drivers sufficiently in advance of the vehicles arrival at a hazard so that even a tired inattentive driver will have time to respond.
Information must not be provided so far in advance that a tired driver will forget that action is required.
2. Discussion of Prior Art
The enhancement of highway traffic safety and the associated improvement in highway capacity that results from reduction of accident related delays has commanded the attention of inventors for many years. As summarized in the Department of Transportation "IVHS Architecture Development Program" report of April 1994, efforts have often been directed toward providing an array of sensors on vehicles that will detect the proximity of other vehicles and warn the driver, for example, that he is too close to the vehicle ahead or that there is a vehicle in an adjacent lane. In one suggested design there are 8 radiating sensor elements and displays on a given vehicle which are intended to provide protection against collision. Systems of this type have been field tested and even deployed on critical vehicles such as school buses. In general, they have been proven to be impractical for the following reasons.
a--Acoustic or R.F. vehicle mounted sensors can determine spatial relationships of immediately adjacent vehicles but they cannot determine activity of vehicles that are several vehicles in front of or behind the instrumented vehicle nor can they adequately detect intrusion by side street vehicles. They are therefore ineffective in preventing multi-car pile ups and intersection collisions. PA1 b--Vehicle mounted sensors can, to a limited extent, advise the driver of the instrumented car that he should modify his behavior in order to avoid hazards but they do not prevent the drivers of non-instrumented vehicles from creating hazardous situations that will adversely affect the instrumented vehicle. For example, it is small consolation for a driver to know that he is about to be rear ended by a vehicle that cannot stop behind him. All he can do is brace himself and hope for the best. PA1 c--In normal congested multi-lane highway traffic, vehicle mounted sensors and the associated software generate such a high false alarm rate that drivers simply ignore them. PA1 d--The combination of vehicle mounted sensors that might reasonably mitigate all possible accident situations is so complex and costly that they could not be expected to be on a large percentage of vehicles nor are they likely to be mandated by Federal authorities. PA1 a--Until the inventions of Spiess U.S. Pat. No. 5,264,854 and Spiess U.S. Pat. No. 5,278,563 and my copending application Ser. No. 08/179,521, off vehicle systems lacked the required accuracy in terms of vehicle location and speed. They also lacked the ability to operate satisfactorily in very dense vehicle environments and were effective only in detecting specially equipped vehicles. PA1 b--Software presently in existence is not capable of analyzing a complex data stream of multiple vehicle position and velocity information and in turn deriving low false alarm probability safety advisory information that can be communicated to the drivers of many vehicles operating along a monitored highway. PA1 a--to provide digital processing means that accepts closely spaced multiple vehicle range and velocity data and establishes track files on each vehicle that includes a time history of the vehicle's location, velocity, acceleration and identification. PA1 b--to provide digital data processing means which operate on the track file data and which determine if and when specific vehicles are approaching a hazardous situation. PA1 c--to provide further digital processing means which generate warnings and advisories that precede a vehicle's arrival at a hazardous situation by an interval of time that exceeds the corrective action response time of drivers. PA1 d--to provide means for formatting the commands and advisories so that they can be communicated to the infrastructure of existing and newly developed traffic signals and driver communication devices. PA1 e--to provide means for formatting the commands and advisories so that they can be addressed to specific vehicles that can benefit from the information.
Recognizing the limitations of vehicle mounted sensors, various attempts have been made to use off vehicle devices. These attempt to monitor traffic with sufficient precision to allow effective, low false alarm rate advisories to be communicated to drivers. They have failed for two reasons: